ABNORMAL BLOOD-GROUP-SS-ACTIVE SIALOGLYCOPROTEINS IN THE MEMBRANE OF MILTENBERGER CLASS-III, CLASS-IV AND CLASS-V HUMAN-ERYTHROCYTES

The authors have studied the inherited changes occurring in the sialoglycoproteins of membranes from erythrocytes of type Miltenberger Class III (Mi.III), Miltenberger Class IV (Mi.IV) and Miltenberger Class V (Mi.V) by using sodium dodecyl sulphate/polyacrylamide gel electrophoresis and lactoperoxidase radioiodination. Mi.III erythrocytes lack the normal blood-group-Ss-active sialoglycoprotein but contain an unusual s-active sialoglycoprotein of higher apparent molecular weight. A similar abnormal S-active sialoglycoprotein appears to occur in Mi.IV erythrocytes. The Mi.V condition is associated with the hemizygous absence of both the normal blood-group-MN-active sialoglycoprotein and the normal Ss-active sialoglycoprotein. However, a new sialoglycoprotein component is present in these cells that has properties characteristic of both the MN-active and Ss-active sialoglycoproteins. The results suggest that the new sialoglycoprotein present in Mi.V erythrocytes is a hybrid of the normal MN sialoglycoprotein and an s-active sialoglycoprotein that has properties similar to the s-active sialoglycoprotein found in Mi.III erythrocytes. This suggested that the unusual Mi.V sialoglycoprotein is derived from chromosomal misalignment with unequal crossing-over between the genes for the MN- and Ss-active sialoglycoproteins in a manner similar to that which gives rise to haemoglobin Lepore. Further studies of S-s-erythrocytes confirm that these cells lack normal Ss-active sialoglycoprotein, but contain an unusual component that shows some of the properties of the normal Ss-active sialoglycoprotein. Analysis of erythrocytes of type M(k)/Mi.III confirms that, in addition to the known hemizygous lack of the MN-active sialoglycoprotein, the M(k) condition is also associated with a loss of the Ss-active sialoglycoprotein. In order to facilitate discussion of the complex changes that occur in these variant erythrocytes, a new unified nomenclature is used for the erythrocyte sialoglycoproteins.